This invention relates to couplings for rotating components such as an electric generator shaft and a gearbox and in particular to a tribological coating system for use on such couplings.
FIGS. 1A and 1B show typical components of a coupling assembly for coupling an electric generator shaft to a gearbox. The assembly includes a sleeve 10 having an axially extending portion 12 and a flange portion 14. The axially extending portion 12 has a generally square cross-section with the four corners beveled. The axially extending portion 12 is inserted into a hollow section of an electric generator shaft having the same cross-sectional shape. Also part of the assembly is a drive shaft 20. The drive shaft 20 has a splined portion 22 for engaging corresponding splines in a gearbox. It also has an axially extending shaft portion 24 shaped and sized to be inserted into the sleeve 10.
During prolonged usage at high speeds and temperatures, this prior art coupling assembly will experience wear on the contacting surfaces. This wearing may result in the binding of the shaft portion 24 and/or the tearing of the sleeve 10.
Accordingly, there exists a need for a coupling assembly having a tribological system that can operate at high temperatures and speed.
An object of the present invention is to provide a coupling assembly having a tribological system that can operate at high temperatures and speed.
The present invention achieves this object by providing a coupling with a tribological system that can withstand temperatures up to 600xc2x0 C. The coupling includes a shaft having an outer surface with a layer of chromium and a sleeve for receiving the shaft. The sleeve has an inner surface coated with a layer of silver or gold. The silver or gold layer contacts the chromium layer to form the tribological system.
These and other objects, features and advantages of the present invention are specifically set forth in or will become apparent from the following detailed description of a preferred embodiment of the invention when read in conjunction with the accompanying drawings.